The invention relates to dust bags to be used primarily in vacuum cleaners. More particularly, the invention refers to dust bags provided with an intake opening for receiving a socket piece of a vacuum cleaner or the like. Further, the invention relates to methods of producing such dust bags.
Collection equipment for dust and similar materials, such as vacuum cleaners, requires the use of containers or bags for the material to be collected. These bags can consist of paper or any other filtration type material which on the one hand allows to collect the dust and dust-like material and on the other hand has a porosity sufficient for the fluid carrying the dust or dust-like material to penetrate through the walls of the filter-like material with a minimum pressure drop. The materials are well known to the artisan in the field.
Typically these dust bags are provided with a single intake opening through which the dust or dust-like material is to be transported and collected within the bag. For a number of reasons, this opening should preferably be reinforced by a suitable means. Most typically this is achieved through the use of a mounting means for mounting the dust bag at the socket piece. Such mounting means or so-called collars have an opening most typically of a circular form which practically corresponds to the opening within the bag. The collar is attached to the bag so that a sealing effect is obtained which prevents the fluid and the dust to pass through openings other than the openings of the dust bag and the collar. The collar consists of a relatively stable material, such as cardboard or plastic.
EP 0 179 950 describes a dust bag and especially methods for attaching a mounting means in a sealing manner by applying adhesive around the opening within the filter bag. The mounting means is designed to receive a socket piece from which dust is discharged and which can be passed through its opening so that the mounting means is slightly stretched and will be fastened in sealing abutment around the socket piece.
DE 28 06 305 describes a vacuum cleaner bag having a collar, and methods for manufacturing said bag. Also here a collar is sealingly attached to the bag through the use of an adhesive.
DE 24 16 079 describes a similar configuration in which dust bags are used that are folded in a special manner and are provided with an opening onto which the collar is attached, again through the use of an adhesive.
DE 23 10 160 relates to a method in which a hose consisting of the above described filter material is produced in a continuous process wherein pieces of this hose are cut off and their ends are folded and sealed in order to form a completely closed bag. On one side of this bag, an opening for sealing attachment of a collar therein is formed in one layer.
JP 8-38402 and JP 8-38403 relate to a so-called three-dimensional bag which has folded wall portions as e.g. illustrated in FIG. 3 of JP 8-38402 which can be obtained from a four-sided bag with open ends wherein two opposing wall portions are folded inwardly. In one of the two others unfolded wall portions an opening is provided onto which a collar can be attached. The two ends are then closed and sealed. The dust bag is folded along a center line extending perpendicularly to the sealed ends through the collar and the opening therein and is formed in one of the wall portions. The collar may extend beyond one of the sealed ends.
In all of the known filter bag designs the opening is provided in one of the wall portions of the hose of the filter material established by the wall portions. This provision of the opening is rather complicated to manufacture. Filter bags of the described type are typically disposable items. Therefore, it is essential to minimize both the material consumption and the overall manufacturing cost.
It is an object of the invention to provide a dust bag and methods to produce dust bags in a simple manner requiring only few manufacturing steps. This object is solved by a dust bag according to claim 1 and by methods for manufacturing dust bags according to claims 11 and 14.
According to the invention a dust bag for collecting dust-like material, particularly for vacuum cleaners, with at least two opposing wall portions of filter material and with an intake opening is provided, wherein the two wall portions are connected to each other and define an outer edge of the dust bag; the wall portions each have a recess which is open to the outer edge; the recesses of the wall portions are identical in shape and size and opposed to each other in the overlaying state of the wall portions, and the two recesses of the wall portions form the intake opening.
According to the invention, the dust bag comprises at least two wall portions of filter material which in an overlaying state are opposed to each other. The two opposing wall portions are connected to each other at one outer edge of the dust bag. Each wall portion has a recess that is open to the aforementioned edge. The two recesses are identical in shape and size and opposed to each other in the overlaying state. When using the dust bag, the dust bag is unfolded from its overlaying state into an unfolded state. In this state, the two recesses form the intake opening for receiving the socket piece. The remaining edges of the dust bag are also connected to each other. The edges are obtained by connecting two adjacent wall portions and/or by folding the wall portions.
The wall portions of the dust bag according to the invention can be made from a filtering material selected from the group comprising paper, synthetic material, nonwoven material, in particular of recyclable polypropylene, as known to someone skilled in the art.
Since the recesses are opposed to each other in the overlaying state, they can be cut into the wall portions within one manufacturing step. Each recess forms a half of the intake opening.
Preferably, the intake opening of the dust bag is surrounded by a mounting means for mounting the dust bag to the socket piece. By insertion of the socket piece into and through the intake opening of the dust bag, the mounting means due to its dimensions can be frictionally seated, thus fixing the dust bag sealingly to the socket piece. According to the invention, the mounting means comprises at least two mounting elements. Each element is fixed to one of the two opposing wall portions and arranged adjacent to the common edge of the two wall portions. Thus, the mounting elements are opposed to each other in -the overlaying state. In the unfolded state of the dust bag, the mounting elements are arranged in one plane and form the so-called collar. A sealing element may be arranged e.g. by adherence at the inner edge of the collar for sealing the mounting element to the socket piece.
In a preferred embodiment of the dust bag, the two mounting elements are flexibly connected to each other. The two mounting elements are connected e.g. via a thin foil. Preferably, the two mounting elements are connected via a spacer element. The spacer element has a width corresponding to the thickness of the wall portions being arranged between the mounting elements in the overlaying state. Thus, the dust bag is relatively flat in the overlaying state and can be stored easily. The spacer element is flexibly connected to each of the two mounting elements.
The mounting means can be made of one piece. To provide a mounting means having two flexibly connected mounting elements, the one-pieced mounting means can be cut along a symmetry axis wherein the depth of the cut is less than the thickness of the mounting means. Another possibility to manufacture a mounting means out of one piece having two flexibly connected mounting elements is to perforate the mounting means along the symmetry axis. This symmetry axis is in alignment with the common edge of the two wall portions. In both cases described above the one-piece mounting means is provided with a line of weakness and/or a living hinge to facilitate flexibility of the integral connection of the two mounting elements.
If the two mounting elements are connected via a spacer element, the flexible connection between the mounting elements and the spacer element can also be achieved by the aforementioned cutting process or by perforating, i.e. by providing lines of weakness between each of the mounting elements and the spacer element, respectively.
In addition, it is possible to fold the wall portions in a manner providing a three-dimensional dust bag. Furthermore, additional wall portions can be used and connected with the two opposing wall portions to manufacture a three-dimensional dust bag. Each wall portion may comprise one or several layers of gas permeable (filter) material.
A preferred method for manufacturing dust bags according to the invention comprises the steps of overlaying two wall portions of a filter material such that said wall portions are connected along an outer edge of the bag, and cutting recesses into both wall portions within one step, which recesses are open to said outer edge and together form an intake opening.
If desired, after the cutting step, the recesses can be surrounded by a mounting means at opposite sides of the wall portions facing away from each other. For this purpose, mounting means as described above can be used, in particular a mounting means comprising two mounting elements each fixed to one wall portion adjacent to the edges and opposed to each other in the overlaying state of the wall portions. The mounting means having an opening to receive the socket piece can also be fixed to the wall portions before the cutting step is performed.
Another preferred method for manufacturing a dust bag according to the invention combines the manufacture of the recesses in the mounting means and the cutting of the recesses into both wall portions. Thus, after the step of overlaying two wall portions of filter material as described above, a mounting element is fixed to each of said wall portions at the outer side of each wall portion such that both mounting elements are opposed to each other and arranged adjacent to the outer edge of the wall portions. After this step, recesses are cut into both wall portions and both mounting elements in one step. The recesses are open to the outer edge of the wall portions and form the intake opening. Preferably, the mounting elements are already flexibly connected.
Within the first step of the two above-described methods it is possible to supply two sheets of filter material separately to form two opposing wall portions. After this supplying step, the outer edges extending in the supply direction can be connected to each other to form a continuous hose or tube of filter material. Thereafter, the recesses are cut into both of the wall portions or into both of the wall portions and the mounting elements. It is also possible to connect the edges extending in the supply direction, after the cutting of the recesses. Thereafter, the hose having recesses and, if desired, provided with mounting means if desired, is cut into preferably regular intervals. The thus created two additional open sides are connected such that a bag is obtained which has an essentially rectangular shape with all four sides sealed together.
Since a hose or tube is easier to handle, the two opposing wall portions are connected to each other along connecting lines which are vertical to the feeding direction before they are cut into dust bags between these two connecting lines. Thus, a bag with all four sides sealed together is obtained directly after the final cutting step.
Instead of feeding two sheets of filter material separately to form the two opposing wall portions, it is also possible to feed only one sheet of filter material which is folded to form the two opposing wall portions. The folding line extends in the feeding direction. Thereafter, the dust bag is manufactured by one of the above-described various methods.
In any of the described methods according to the invention, it is also possible to form a three-dimensional bag by folding the wall portions as desired or by adding additional wall portions.